Herbicidal amide derivatives

ABSTRACT

New compounds of the formula ##STR1## wherein R 1  and R.sub. 2 each is alkyl; R 3  is a nitrogen-containing heterocyclic group; and R.sub. 4 is optionally substituted phenyl, are useful as herbicides.

This is a division of application Ser. No. 482,935, filed June 25, 1974now U.S. Pat. No. 3,920,675, issued Nov. 18, 1975.

DESCRIPTION OF THE INVENTION

This invention relates to amide derivatives which are of interest asherbicides.

Accordingly the present invention provides amide derivatives of generalformula: ##STR2## wherein R₁ and R₂ each represents an alkyl group; R₃represents a nitrogen-containing heterocyclic group; and R₄ represents aphenyl group optionally substituted by halogen or by alkyl.

More particularly, the invention is directed to amide derivatives ofgeneral formula I wherein R₁ and R₂ each represents an alkyl group of1-6 carbon atoms; R₃ represents a 5- or 6-membered heterocyclic groupcontaining 1 to 2 nitrogen atoms in the ring and 0 to 1 sulfur atoms inthe ring; and R₄ represents a phenyl group optionally substituted byfluorine or chlorine or by an alkyl group of 1-6 carbon atoms.

Because of their properties, preferred amide derivatives are those offormula I wherein R₁ and R₂ each represents an alkyl group of 1-6 carbonatoms, for example methyl, ethyl, or propyl; R₃ represents a 5- to6-membered nitrogen-containing heterocyclic group, for example,thiazolyl, 1,3,4-thiadiazol-2-yl or pyridyl, and R₄ represents a phenylgroup optionally substituted by one or two chlorine atoms or by an alkylgroup of 1-6 carbon atoms, for example by methyl.

The compounds of formula I may be prepared by a process which comprisesreacting a compound of formula: ##STR3## wherein R₅ represents an alkylgroup, with an amine of the formula:

    NH.sub.2 R.sub.3                                           III

when R₅ is an alkyl group the reaction is suitably carried out in thepresence of a strong base, for example an alkali metal hydride such assodium hydride. The compounds of formula II wherein R₅ is alkyl areknown compounds, disclosed in Netherlands Pat. No. 72,07026.

As mentioned above the amide derivatives of the invention are ofinterest as herbicides, and the invention includes, therefore,herbicidal compositions comprising a carrier and/or a surface activeagent, together with, as active ingredient, an amide derivative of theinvention. Likewise the invention also includes a method of combatingweeds at a locus which comprises applying to the locus an amidederivative or composition of the invention.

The term "carrier" as used herein means a solid or fluid material, whichmay be inorganic or organic and of synthetic or natural origin, withwhich the active compound is mixed or formulated to facilitate itsapplication to the plant, seed, soil or other object to be treated, orits storage, transport or handling.

The surface-active agent may be an emulsifying agent or a dispersingagent or a wetting agent; it may be non-ionic or ionic.

Any of the carrier materials or surface-active agents usually applied informulating pesticides may be used in the composition of the invention,and suitable examples of these are to be found, for example, in UKspecification No. 1,232,930.

The compositions of the invention may be formulated as wettable powders,dusts, granules, solutions, emulsifiable concentrates, emulsions,suspension concentrates or aerosols. Wettable powders are usuallycompounded to contain 25, 50 or 75% w of toxicant and usually contain,in addition to solid carrier, 3-10% w of a dispersing agent and, wherenecessary, 0-10% w of stabilizer(s) and/or other additives such aspenetrants or stickers. Dusts are usually formulated as a dustconcentrate having a similar composition to that of a wettable powderbut without a dispersant, and are diluted in the field with furthersolid carrier to give a composition usually containing 1/2-10% w oftoxicant. Granules are usually prepared to have a size between 10 and100 BS mesh (1.676-0.152 mm), and may be manufactured by agglomerationor impregnation techniques. Generally, granules will contain 1/2-25% wactive ingredient and 0-10% w of additives such as stabilizers, slowrelease modifiers and binding agents. Emulsifiable concentrates usuallycontain, in addition to the solvent and, when necessary, co-solvent,10-50% w/v active ingredient, 2-20% w/b emulsifiers and 0-20% w/v ofappropriate additives such as stabilizers, penetrants and corrosioninhibitors. Suspension concentrates are compounded so as to obtain astable, non-sedimenting, flowable product and usually contain 10-75% wactive ingredient, 0.5-15% w of dispersing agents, 0.1-10% w ofsuspending agents such as protective colloids and thixotropic agents,0-10% w of appropriate additives such as defoamers, corrosioninhibitors, stabilizers, penetrants and stickers, and as carrier, wateror an organic liquid in which the active ingredient is substantiallyinsoluble; certain organic solids or inorganic salts may be dissolved inthe carrier to assist in preventing sedimentation or as antifreezeagents for water.

Aqueous dispersions and emulsions, for example, compositions obtained bydiluting a wettable powder or a concentrate according to the inventionwith water, also lie within the scope of the present invention. The saidemulsions may be of the water-in-oil or of the oil-in-water type, andmay have a thick "mayonnaise"-like consistency.

The compositions of the invention may also contain other ingredients,for example, other compounds possessing pesticidal, especiallyinsecticidal, acaricidal, herbicidal or fungicidal properties.

The invention is further illustrated in the following examples. Itshould be understood, however, that the examples are for the purpose ofillustration only and should not be regarded as limiting the inventionin any way. In the examples the structure of the compounds was confirmedby elemental analysis and NMR spectral analysis.

EXAMPLE 1 Preparation of4-Benzyloxymethyl-4-ethyl-2-methyl-1,3-dioxolan-2(N-pyrid-2-yl)carboxamide

Ethyl 4-benzyloxymethyl-4-ethyl-2-methyl-1,3-dioxolan-2-carboxylate(8.0g), 2-amino-pyridine (2.45g) and sodium hydride (1.25g of 50%dispersion in oil) were stirred together in dimethyl sulphoxide (50ml)for 16 hours at room temperature. The reaction mixture was poured ontoice and extracted with chloroform. The organic solution was washed twicewith water, dried and the solvent evaporated. The residue was purified(chromatography on silica gel using chloroform as eluant) to givedesired product 3.1g (33%) as an oil.

Analysis: Calculated for C₂₀ H₂₄ N₂ O₄ : C, 67.4; H, 6.8; N, 7.9%.Found: C, 67.4; H, 7.1; N, 7.8%.

EXAMPLES 2-5

Following procedures similar to those given in the previous Examplefurther compounds were prepared, for which physical characteristics aregiven in the following Table 1.

                                      TABLE 1                                     __________________________________________________________________________                                  m.p.° C                                                                or                                                         Compound           refractive index                                __________________________________________________________________________    2 4-benzyloxymethyl-4-ethyl-2-methyl-1,3-dioxo-                                 lan-2-(N-thiazol-2-yl)carboxamide                                                                         n.sub.D.sup.24 1.5210                           3 4-benzyloxymethyl-2,4-dimethyl-1,3-dioxolan-                                  2-(N-pyrid-4-yl)carboxamide n.sub.D.sup.24 1.5105                           4 4-benzyloxymethyl-4-ethyl-2-methyl-1,3-dioxo-                                 lan-2-(N-5-methyl-1,3,4-thiadiazol-2-yl)carboxamide -                                                     isomer A                                        5 4-benzyloxymethyl-4-ethyl-2-methyl-1,3-dioxo-                                                             m.p.                                              lan-2-(N-5-methyl-1,3,4-thiadiazol-2-yl)carboxamide                                                       137-140                                         __________________________________________________________________________

EXAMPLE 6 Herbicidal Activity

To evaluate their herbicidal activity, compounds of the invention weretested using as a representative range of plants:- maize, Zea mays (Mz);rice, oryza sativa (R): barnyard grass, Echinchloa crusgalli (BG); pea,Pisum sativum (P); linseed, Linum usitatissium (L); mustard, Sinapisalba (M); and sugar beet, Beta vulgaris (SB).

The tests fall into two categories, pre-emergence and post-emergence.The pre-emergence tests involved spraying a liquid formulation of thecompound onto the soil in which the seeds of the plant species mentionedabove had recently been sown. The post-emergence tests involved twotypes of test, viz. soil drench and foliar spray tests. In the soildrench tests the soil in which seedling plants of the above species weregrowing, was drenched with a liquid formulation containing a compound ofthe invention, and in the foliar spray tests the seedling plants weresprayed with such a formulation.

The soil used in the tests was a steam-sterilized, modified John InnesCompost mixture in which half the peat, by loose bulk, had been replacedby vermiculite.

The formulations used in the tests were prepared by diluting with watersolutions of the compounds in acetone containing 0.4% by weight of analkylphenol/ethylene oxide condensate available under the trade nameTriton X-155. In the soil spray and foliar spray tests the acetonesolutions were diluted with an equal volume of water and the resultingformulations applied at two dosage levels corresponding to 10 and 1kilograms of active material per hectare respectively in a volumeequivalent to 400 liters per hectare. In the soil drench tests onevolume of the acetone solution was diluted to 155 volumes with water andthe resulting formulation applied at one dosage level equivalent to 10kilograms of active material per hectare in a volume equivalent toapproximately 3,000 liters per hectare.

The herbicidal effects of the compounds were assessed visually sevendays after spraying the foliage and drenching the soil and eleven daysafter spraying the soil, and were recorded on a 0-9 scale. A rating 0indicates no effect on the treated plants, a rating 2 indicates areduction in fresh weight of stem and leaf of the plants ofapproximately 25%, a rating 5 indicates a reduction of approximately55%, a rating 9 indicates a reduction of 95% etc.

The results of the tests are set out in Table 2.

                                      TABLE 2                                     __________________________________________________________________________             Post-Emergence                Pre-emergence                          Dosage   Soil Drench    Foliar Spray   Soil Spray                             Example                                                                            kg/ha                                                                             Mz                                                                              R BG P L M SB                                                                              Mz                                                                              R BG P L M SB                                                                              Mz                                                                              R BG P L M SB                        __________________________________________________________________________    1    10  7 6 8  5 8 3 5 7 4 8  5 7 5 5 9 9 9  9 7 7 7                               1                 2 0 7  5 6 0 5 8 9 9        9                                                                             7                                                                             3                                                                             3                         2    10  7 5 7  4 7 3 6 7 4 8  5 7 2 5 9 9 9        9                                                                             7                                                                             6                                                                             7                               1                 0 0 7  4 7 0 5 8 9 9        8                                                                             7                                                                             5                                                                             3                         3    10  7 3 7  0 0 0 3 3 4 8  7 8 8 4 9 9 9        8                                                                             7                                                                             7                                                                             5                               1                 0 0 1  2 1 2 2 0 6 8        0                                                                             0                                                                             0                                                                             0                         __________________________________________________________________________

We claim as our invention:
 1. An amide derivative of the formula##STR4## wherein R₁ and R₂ each represents an alkyl group of 1 to 6carbon atoms, R₃ represents 1,3,4-thiadiazol-2-yl; and R₄ represents aphenyl group optionally substituted by fluorine or chlorine or by analkyl group of 1 to 6 carbon atoms.
 2. An amide derivative according toclaim 2 wherein R₄ represents a phenyl group optionally substituted byone or two chlorine atoms or by an alkyl group of 1 to 6 carbon atoms.3. A herbicidal composition comprising as active ingredient aherbicidally effective amount of a compound of claim 1 together with atleast one carrier or surface active agent therefore.
 4. An amidederivative according to claim 1 wherein R₁ represents ethyl, R₂represents methyl and R₄ represents phenyl.